Sealing element, annular filter element, oil separator, and method for controlling prevailing pressure in crankcase ventilation system

ABSTRACT

An annular filter element and sealing element for an oil separator of a crankcase ventilation system, the filter element has a covering surface extending parallel to a direction of flow, together with at least one cover element covering surface in at least some regions. An oil separator is taught having the filter element with at least one pressure control valve controlling crankcase pressure and has a valve closing body that operates in conjunction with a valve seat. The sealing element having at least one radially sealing region that is configured to act in the direction of the radius of the annular filter element, and at least one axially sealing region that is configured to act in the direction of the longitudinal axis of the annular filter element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.15/169,932, filed 1 Jun. 2016, which claims a priority date of 1 Jun.2015 based upon prior filed German patent application No. DE102015006767.2, filed 1 Jun. 2015. The entire contents of the aforesaidU.S. application Ser. No. 15/169,932 and the German patent applicationNo. DE 102015006767.2 being incorporated herein by reference to thefullest extent permitted by the law.

This application is a Continuation of U.S. application Ser. No.16/278,129, filed 17 Feb. 2019, which is a Divisional of U.S.application Ser. No. 15/169,848, filed 1 Jun. 2016, Now U.S. Pat. No.10,221,736 B2, which claims a priority date of 1 Jun. 2015 based uponprior filed German patent application No. DE 102015006768.0, filed 1Jun. 2015. The entire contents of the aforesaid U.S. application Ser.No. 16/278,129, the aforesaid U.S. application Ser. No. 15/169,848 andthe German patent application No. DE 102015006768.0 being incorporatedherein by reference to the fullest extent permitted by the law.

TECHNICAL FIELD

The invention relates to a sealing element for a replaceable filterelement of an oil separator of a crankcase ventilation system and to anoil separator, as well as a method. The invention further relates to afilter element for an oil separator, an oil separator of a crankcaseventilation system, and a method for controlling the prevailing pressurein a crankcase ventilation system.

BACKGROUND

With reciprocating piston internal combustion engines, an oil-containingleakage gas, so-called blow-by, is produced in the crankcase. The returnthereof into the combustion process is legally mandated worldwide, andtakes place in so-called closed crankcase ventilation systems. The mostimportant tasks of a crankcase ventilation system are oil separation andoil return into the crankcase, as well as the regulation of thecrankcase pressure. The requirements for oil separation have beensteadily increasing in recent years, as legislation on emissions hasgrown increasingly stringent, in order to protect emissions-relatedengine components such as exhaust gas turbochargers, intercoolers, orsensors from performance loss due to oil contamination. Thus, oilseparation is important not only in minimizing oil consumption, but alsoin making what is now an essential contribution to compliance withemissions legislation throughout the lifetime of the vehicle. Inaddition to oil separation, a crankcase ventilation system containsother important components, such as, for example, a pressure controlvalve, depending on the ventilation design.

In order to extend the life of the return spring in a pressure controlvalve for an internal combustion engine, DE 10 2004 02 22 75 A1 proposesarranging the return spring on the side of the valve closing body facingaway from the valve seat, and thus preventing the return spring fromcontacting aggressive blow-by gases emerging from the crankcase.Documents WO 2007 13 50 82 A2 and JP 2003 33 65 16 A disclose arrangingthe return spring on the atmosphere side of a pressure control valve.

The crankcase ventilation has two spaces that must be separated from oneanother—namely, a pre-filtration side, on which the not-yet-cleanedblow-by gas is located, and a post-filtration side, on which the cleanedgas is located.

In addition to separating and sealing off the pre-filtration side fromthe post-filtration side, the pre-filtration side and post-filtrationside must additional be separated and sealed off from the atmosphere.These three sealing functions are performed, in the prior art,predominantly by three individual seals, for example, three individualO-rings or three individual molded seals.

In addition to individual seals, each of which fulfills only one sealingfunction, so-called combined seals that fulfill more than one sealingfunction are also known in the prior art. Thus, EP 2 272 580 A1discloses a combined seal (cf. reference sign 25 of the FIG. 1 in EP 2272 580 A1) for a filter insert of a crankcase ventilation system,wherein this combined seal comprises two continuous sealing elementsthat each act in the radial direction of the filter insert and arespaced apart axially from one another.

In addition, DE 10 2010 063 161 A1 discloses a fluid filter devicehaving a radially-acting combined seal. This combined seal acts betweenan annular filter element and a dome mounted coaxially onto the annularfilter element, and fulfills two sealing functions. On the one hand,this combined seal seals the pre-filtration side of the fluid filterdevice against backflow, while on the other hand, the combined sealseals the pre-filtration side of the fluid filter device from thepost-filtration side of the fluid filter device.

DE 20 2006 017 61 U1 discloses a liquid filter having a radially-actingseal that seals an upper end plate of an annular filter element off fromthe tube body of a support dome configured in order to support theannular filter element.

SUMMARY

The invention addresses the problem of developing a filter element ofthe aforementioned type, an oil separator of the aforementioned type,and a method of the aforementioned type, in such a manner that thefunctions thereof are optimized, in particular, that the crankcaseventilation system takes up the least installation space possible.

The invention is based on realizing the functions of the crankcaseventilation system with the fewest possible components.

According to the invention, the cover element of the filter elementcomprises at least one clean fluid discharge element that: leads outfrom the interior of the filter element; in particular, extends awayfrom the filter element; in particular, is tube-shaped; and isconfigured in order to remove the purified fluid, in particular, cleanair. The end surface of this clean fluid discharge element that facesaway from the filter element is configured as a sealing surface for avalve of the crankcase ventilation system, or comprises a sealingsurface for a valve of the crankcase ventilation system. Preferably, thesealing surface is a valve seat for a valve closing body, in particular,for a valve closing body sealing element of a pressure control valvethat surrounds the valve closing body. In addition to the function ofdischarging or removing the purified fluid, the clean fluid dischargeelement thus assumes another function, namely, a sealing function.

The sealing surface is substantially flat and free of burrs, wherein theends, margins, or edges of the sealing surface may be rounded. Inaddition, the sealing surface is preferably round, in particular,circular.

The arrangement of the sealing surface on the clean fluid dischargeelement, as described, causes the sealing surface and the plane definedthereby to be preferably spaced apart from the axial, outer surface ofthe cover element. This arrangement likewise defines the distance of thevalve from the cover element. Within this distance, the clean fluidoutlet of the oil separator housing, in which the filter element is tobe incorporated, can be advantageously arranged so as to conserveinstallation space. For a streamlined overall design, it is thereforepreferred that the length of the clean fluid discharge element, asmeasured from the axial, outer surface of the cover element, correspondsapproximately to the diameter of the clean fluid outlet of the oilseparator housing.

The present invention is based on providing an all-in-one sealingelement that fulfills both a radial sealing function and an axialsealing function, wherein the radially sealing region and the axiallysealing region are configured so as to be continuous.

“Radial” means here in the direction of the radius of the annular filterelement. “Axial” means here in the direction of the longitudinal axis ofthe annular filter element.

Advantageously, the oil separator has a filter housing configured inorder to accommodate the annular filter element. This filter housingadvantageously has a round—for example, circular or oval—cross-section.

In a particularly advantageous embodiment of the present invention, theaxially sealing region is arranged between two parts of the filterhousing, and the radially sealing region is arranged within the filterhousing.

The interior of the filter housing is divided by the annular filterelement into a pre-filtration space or pre-filtration side containingunfiltered fluid, and a post-filtration space or post-filtration sidecontaining filtered fluid.

In a particularly advantageous embodiment of the present invention, thesealing element comprises the two sealing regions—namely, the radiallysealing region and the axially sealing region—in order to seal thepre-filtration side of the oil separator off from the post-filtrationside of the oil separator, and in order to seal the interior of the oilseparator off from the environment.

For example, the radially sealing region may be configured so as to sealoff the pre-filtration side from the post-filtration side, and theaxially sealing region is configured so as to seal the interior of thefilter housing off from the environment or from the atmosphere.

In this particularly advantageous embodiment of the present invention,the sealing element is configured so as to fulfill three sealingfunctions or sealing tasks in the operating position thereof, namely:

-   -   a) sealing the pre-filtration side off from the atmosphere,    -   b) sealing the post-filtration side off from the atmosphere, and    -   c) sealing the post-filtration side off from the pre-filtration        side.

In order to functionally decouple the radially sealing region and theaxially sealing region, the radially sealing region advantageously isarranged at an, in particular, axial and/or radial distance from theaxially sealing region. In this manner, the two sealing regions arefunctionally independent, but integrated into one part. For example, inthis manner, the sealing function of the sealing of the pre-filtrationside or the post-filtration side from the atmosphere can be decoupledfrom the sealing function of the sealing of the post-filtration sidefrom the pre-filtration side. The spacing apart of the sealing regionsis advantageously achieved by means of a connecting strut that connectsthe two sealing regions. The connecting strut preferably has the shapeof a short, tube-shaped hollow cylinder section. This may preferably berelatively thin, e.g., thinner than the cross-sections of the sealingregions. The connecting strut may also have an L-shaped cross-section.This signifies that from the aforementioned hollow cylindrical shape,which forms one leg of the L, another leg protrudes radially inward oroutward, thus forming a circular annular disc-shaped second connectingstrut section. This makes it possible to have another radial distance,preferably in addition to the axial distance, between the sealingregions. This makes it possible for a housing upper part or cover in anarrow installation region to provide independent sealing surfacescorresponding to the sealing regions, e.g., by the housing upper part orhousing cover also having a cross-section that is also L-shaped insections in the region of the sealing element, wherein the axial legprovides a contact surface for the radially sealing region and theradial leg provides a contact surface for the axially sealing region ofthe sealing element.

A distance between the radically sealing region and the axially sealingregion also makes it possible to arrange the radially sealing regionwithin the filter housing of the oil separator and arrange the axiallysealing region between two housing parts or housing halves of the filterhousing of the oil separator.

Advantageously, the radially sealing region and the axially sealingregion are arranged at an offset to one another in the direction of thelongitudinal axis of the annular filter element; in particular, theradially sealing region may be arranged above the axially sealing regionso as to follow the direction of flow of the fluid to be filtered.

Advantageously, the axially sealing region has, on the side thereoffacing away from the radially sealing region, a cylinder tube-shapedcontinuation that has an insertion slope at the end on the outside. Thissimplifies installation of the sealing element or a filter element withsuch a sealing element in a corresponding housing.

In order to remove the filtered clean fluid, a first or upper housingpart of the filter housing advantageously has a clean fluid outlet.Advantageously, the radially sealing region of the sealing element isarranged at the same height as the first or upper housing part, inparticular, as the clean fluid outlet. This makes it possible todismount the upper housing part from another housing part, inparticular, from a housing body configured in order to accommodate theannular filter element, by movement of the upper housing part by meansof a tilting movement or by means of a rotational movement about an axisof rotation running perpendicular to the longitudinal axis of theannular filter element. In the prior art, however, the first or upperhousing part can only be dismounted by means of an axial movement, i.e.,a movement along the longitudinal axis of the annular filter element.The opening of the filter housing by means of a tilting movement makesit easier to replace the annular filter element, because the first orupper housing part can be supported on the housing edge of theadditional housing part, in particular, the housing body.

In order to seal the interior of the filter housing off from theenvironment or from the atmosphere, the axially sealing regionadvantageously can be arranged between the first or upper housing partand the additional housing part—in particular, the housing bodyconfigured in order to accommodate the annular filter element—in such amanner that the axially sealing region is compressed between the firstor upper housing part and the housing body by means of a defined force.

In order to separate oil from fluid, in particular, from an aerosol, theannular filter element advantageously has at least one filter mediumthat is arranged in the shape of a ring, in particular, a circular ringor oval ring, for example, by being wrapped.

As a filter medium, it is possible to use, for example, papers ornon-woven fabrics made of metal fibers, glass fibers, or plastic fibers,in particular, polyester fibers. It would also be possible to combinethese materials. In addition, as described in DE 10 2011 016 893 A1, thefilter medium may be a coalescence medium.

In order to form the filter medium so as to be as stable as possibleagainst forces acting on the filter medium from the outside, the filtermedium advantageously has an oval, in particular, circularcross-section. In an advantageous embodiment of the crankcaseventilation system, the housing of the crankcase ventilation system thatis formed of at least one housing part and configured in order toaccommodate the filter medium also has an oval, in particular, circularcross-section.

The filter medium has a covering surface extending parallel to thedirection of flow of the fluid flowing through the filter medium, and atleast one end plate arranged on the covering surface.

This end plate is advantageously configured to separate thepre-filtration side of the filter housing, in particular, of the housingbody from the post-filtration side of the filter housing, in particular,of the first or upper housing part.

The sealing element advantageously can be releasably or non-releasablyfastened to the end plate. If the sealing element is fasted to the endplate, the sealing element can be replaced together with the annularfilter element when the annular filter element is replaced, in one step.Another advantage of the fastening of the sealing element on the annularfilter element is that the sealing element can be pre-assembled at thefactory, thus avoiding operation errors when the sealing element isbeing replaced.

In order to fasten the sealing element to the filter element, the endplate may have a fastening contour, in particular, a groove, in whichthe radially sealing region of the sealing element can be arranged, inparticular, clamped. Alternatively, the sealing element may be attachedto the end plate in a two-component injection molding process.

Alternatively to the fastening at the end plate, the sealing element mayalso be fastened to the first or upper housing part of the filterhousing. Thus, the sealing element may be tied up into the upper housingpart, or the upper housing part may be encapsulated by the sealingelement.

In order to stabilize the sealing element, the end plate may have asupport contour extending in the direction of the longitudinal axis ofthe annular filter element. This support contour is configured so as toguide and/or keep a side—for example, a tab—of the axially sealingregion of the sealing element that faces the annular filter element.This makes it possible to prevent the sealing element—in particular, aregion or tab of the axially sealing region—from moving toward thefilter medium so as to follow the direction of flow of the fluid, andfolding inwards.

The radially sealing region advantageously can be arranged between thefilter housing—in particular, the first or upper housing part—and theannular filter element-in particular, the end plate of the annularfilter element—in such a manner that the radially sealing region iscompressed radially between the filter housing and the annular filterelement—in particular, between the upper housing part and the endplate—by means of a defined force.

In order to compress the radially sealing region between the filterhousing and the annular filter element—in particular, between the upperhousing part and the end plate—by means of a defined force, the upperhousing part is preferably configured so that the upper housing partsurrounds at least one region of the annular filter element—inparticular, the end plate of the annular filter element, in particular,the annular groove—in the operation position thereof in such a mannerthat the upper housing part forms the counterpart to the seal (see FIGS.2 and 3 ).

In one embodiment in which the radial sealing region and the axialsealing region are compressed by means of a defined force, as describedabove, the sealing element may, in the operation position thereof:

-   -   seal the interior of the first or upper housing part, in        particular, the post-filtration side, off from the environment;    -   seal the interior of the housing body, in particular, the        pre-filtration side arranged between the annular filter element        and the housing body, from the environment; and    -   seal the pre-filtration side off from the post-filtration side.

In a preferred embodiment, the cover element of the (annular) filterelement comprises at least one clean fluid discharge element that: leadsout from the interior of the filter element; in particular, extends awayfrom the filter element; in particular, is tube-shaped; and isconfigured in order to remove the purified fluid, in particular, cleanair. The end surface of this clean fluid discharge element that facesaway from the filter element is configured as a sealing surface for avalve of the crankcase ventilation system, or comprises a sealingsurface for a valve of the crankcase ventilation system. Preferably, thesealing surface is a valve seat for a valve closing body, in particular,for a valve closing body sealing element of a pressure control valvethat surrounds the valve closing body. In addition to the function ofdischarging or removing the purified fluid, the clean fluid dischargeelement thus assumes another function, namely, a sealing function.

The sealing surface is substantially flat and free of burrs, wherein theends, margins, or edges of the sealing surface may be rounded. Inaddition, the sealing surface is preferably round, in particular,circular.

The arrangement of the sealing surface on the clean fluid dischargeelement, as described, causes the sealing surface and the plane definedthereby to be preferably spaced apart from the axial, outer surface ofthe cover element. This arrangement likewise defines the distance of thevalve from the cover element. Within this distance, the clean fluidoutlet of the oil separator housing, in which the filter element is tobe incorporated, can be advantageously arranged so as to conserveinstallation space. For a streamlined overall design, it is thereforepreferred that the length of the clean fluid discharge element, asmeasured from the axial, outer surface of the cover element, correspondsapproximately to the diameter of the clean fluid outlet of the oilseparator housing.

The cover element is preferably an end plate of the filter element. Thecover element is sealingly and non-releasably connected to the filtermedium at an end face of the filter element, for example, by gluing orwelding. The cover element is preferably produced from thermoplasticpolymer, preferably by injection molding.

The clean fluid discharge element is preferably non-releasably (i.e., soas not to be non-destructively removable) and sealingly connected to thecover element, so that the pre-filtration side is separated from thepost-filtration side. The clean fluid discharge element is particularlypreferably integral with the cover element.

The clean fluid discharge element and the cover element are preferablycontinuously closed. This means that the clean fluid discharge elementand the cover element are connected and designed such that other thanthe clean fluid exit opening surrounded by the sealing surface, no otheropenings are present in the cover element or clean fluid dischargeelement.

The clean fluid discharge element is preferably an oval cylindrical, inparticular, circular cylindrical, in particular, straight tube. Thistube comprises a closed cylindrical wall and two open ends, wherein thesealing surface is configured on one end that faces away from the coverelement, and the other end is connected to the cover element, so that afluid connection to the interior of the filter medium or filter body isformed. The ends are preferably oriented so as to be perpendicular tothe central axis.

In a particularly preferred embodiment, the cover element is an annularend plate away from which the clean fluid discharge element, configuredas a tube, extends on the side facing away from the filter medium.

The clean fluid element and the cover element preferably form anL-shaped or T-shaped cross-section.

A preferred embodiment of the filter element of the present inventioncomprises a clean fluid discharge element having an end surfaceconfigured so as to be flat and/or free of burrs in so as to be usableas a sealing surface, in particular, as a valve seat for a valve closingbody of a pressure control valve of the crankcase ventilation system.

A person skilled in the art will appreciate the filter element of thepresent invention, in particular, in use in a crankcase ventilationsystem having an integrated pressure control or integrated pressurecontrol valve. Namely, by means of the sealing surface according to theinvention, the filter element may assume another function beyondseparating oil from aerosol—namely, a partial function of the pressurecontrol. The sealing surface of the filter element may then serve as avalve seat for the valve closing body of the pressure control valve. Thesealing surface may also be configured in order to operate inconjunction with the control of the crankcase pressure, in particular,the limitation of the vacuum of the crankcase ventilation system.

The sealing surface of the filter element of the present invention makesit possible to significantly reduce the installation space for thecrankcase ventilation system in comparison to, for example, prior artdisclosed in documents DE 10 2013 005 624 A1 and WO 2005 088 417 A1, inwhich the valve seat of the pressure control valve is arranged on ahousing side wall of the crankcase ventilation system. Thus, due to thesealing surface of the filter element according to the invention, thecomponents of the pressure control valve, which is configured in orderto control the crankcase pressure, can be accommodated in the upperhousing part of the crankcase ventilation system.

A further reduction of the installation space can be achieved bydesigning the filter element so that the flow therethrough goes from theoutside to the inside and so as to have a cavity configured in order toremove the purified fluid, in the interior of the filter medium. Thus,as opposed the prior art, in which the flow through is from the insideto the outside, it is not necessary to provide a channel by means ofwhich the fluid can be delivered to the interior of the filter medium.

The cavity arranged in the interior of the filter medium and configuredin order to remove the fluid is advantageously connected directly to theclean fluid discharge element or transitions directly into a cavity ofthe clean fluid discharge element that is configured in order to removethe fluid.

In order to form the filter medium so as to be as stable as possibleagainst forces acting on the filter medium from the outside, the filtermedium advantageously has an oval, in particular, circularcross-section. In an advantageous embodiment of the crankcaseventilation system, the housing of the crankcase ventilation system thatis formed of at least one housing part and configured in order toaccommodate the filter medium also has an oval, in particular, circularcross-section.

As the filter medium, it is possible to use basically any material, inparticular, a nonwoven fabric, for example, made of metal fiber, glassfiber, and/or plastic fiber, for example, made of polyester. It wouldalso be possible to combine these materials. In addition, as describedin DE 10 2011 016 893 A1, the filter medium may be a coalescence medium.Preferably, the filter element is an annular coalescence element. Forthis purpose, the filter element preferably has a filter mediumconfigured as a nonwoven fabric that preferably is wrapped repeatedlyand thus in a plurality of layers annularly around a support tube. Thismeans that the filter medium is preferably configured as at least onenon-woven wrap. To stabilize and seal off, a cover element that ispreferably configured as an end plate is also provided on respective endfaces.

The oil separator is preferably configured, as described, as acoalescing filter. The crankcase ventilation system may be configured asa closed crankcase ventilation system in which the post-filtrationleakage gas is returned to the combustion process, or as an opencrankcase ventilation system.

The sealing surface of the filter element is particularly stable and isparticularly easy to produce if the sealing surface, the clean fluiddischarge element, and the cover element are integral with one another,as is preferred.

Independently thereof or in connection thereto, in a preferredembodiment of the filter element of the present invention, the sealingsurface and/or the end plate is made of a mechanically fixed and/orrigid material, for example, polyamide 66 having 35% glass fibers (PA 66GF35).

In order to improve the tightness of the sealing of the pressure controlvalve, the valve closing body has at least one elastic valve closingbody sealing element, at least on the region thereof that can bearranged in contact with the valve seat of the filter element.

The sealing element of the valve closing body advantageously hassubstantially at least one elastomer. In particular, the valve closingbody sealing element may be formed of at least one elastomer, forexample, ethylene acrylate rubber (EAR) and/or from, in particular,hydrogenated nitrile rubber ([H]NBR) and/or acrylate rubber. Incomparison to the prior art, in which the sealing off of the valve seatand the valve closing body is performed solely by hard components, thetightness of the seal of the pressure control valve may be considerablyimproved by the elastic configuration of the valve closing body sealingelement.

In an advantageous embodiment of an oil separator of the presentinvention, the sealing happens from soft to hard. Thus, for example, thevalve closing body and the clean fluid discharge element, in particular,the valve seat are formed essentially out of polyamide 66 with 35% glassfiber (PA 66 GF35) and the valve closing body sealing element is formedessentially out of ethylene acrylate rubber (EAR) and/or acrylaterubber.

The tightness of the seal of the pressure control valve can also beimproved by connecting the sealing element of the valve closing bodyfixedly or non-releasably to the valve closing body, in particular,application to the valve closing body by means of at least one sprayprocess. The valve closing body sealing element and the valve closingbody thus advantageously form a unit. In one advantageous embodiment ofthe present invention, the valve closing body sealing element is nottied up into the valve body, as is known in the prior art, but ratherthe valve body is encapsulated by the valve closing body sealingelement, and forms a solid unit with the valve closing body sealingelement.

Another limiting criterion of an advantageous embodiment of an oilseparator of the present invention relative to the prior art is thusthat the valve closing body and the valve closing body sealing elementare fixedly connected to one another. The valve closing body sealingelement thus forms a solid unit with the valve closing body, whichimproves the tightness of the seal.

A particularly high tightness of the seal of the pressure control valvemay also be achieved by configuring the valve closing body so as to beflat or level at a region thereof that faces the valve seat, inparticular, a region thereof that can be arranged in contact with thevalve seat of the filter element. In contrast, in the prior art, thevalve closing body is usually curved in the shape of a dish on theregion thereof that faces the valve seat. In contrast to the dish shapein the prior art, the valve closing body—in particular, the valveclosing body sealing element—of an optimized embodiment of an oilseparator of the present invention thus has a flat or level shape,whereby the sealing properties are greatly improved.

Independently thereof or in connection therewith, a particularlyadvantageous embodiment of an oil separator of the present invention hasan advantage over the prior art, for example, that is illustrated inFIG. 12 , in that the components of the pressure control valve or thepressure control are located in the upper part of the housing.

An advantageous special feature of the present invention is that theunit filter element can constitute, in particular, the end position forthe valve closing body.

Another special feature of the present invention is that the filterelement can preferably assume two functions:

-   -   1. Separating oil from the gas    -   2. Partial function of the pressure control

BRIEF DESCRIPTION OF THE DRAWINGS

As already discussed above, there are several approaches toadvantageously embodying and developing the teaching of the presentinvention.

FIG. 1 illustrates a perspective view of an embodiment of a crankcaseventilation system according to the present invention, having a pressurecontrol valve;

FIG. 2 illustrates a longitudinal depiction of a crankcase ventilationsystem from FIG. 1 , with an embodiment of an oil separator having afilter element and a sealing element according to the present invention;

FIG. 3 illustrates a longitudinal view of a detail of the oil separatorfrom FIG. 2 ;

FIG. 4 illustrates a plan view of the oil separator from FIG. 2 ;

FIG. 5 illustrates a perspective view of the valve closing body and thevalve closing body sealing element of the pressure control valve of theoil separator from FIG. 2 ;

FIG. 6 illustrates a longitudinal view of the valve closing body and thevalve closing body sealing element from FIG. 2 ;

FIG. 7 illustrates a perspective view of the valve closing body, areturn spring, and a pressure control insert of the oil separator fromFIG. 2 ;

FIG. 8 illustrates a perspective exploded view of the components of anembodiment of a filter element having a sealing element according to thepresent invention;

FIG. 9 illustrates a perspective exploded view of the componentsarranged in the housing cover of the crankcase ventilation systemdepicted in FIG. 1 ;

FIG. 10 illustrates a detail of the pressure control valve of thecrankcase ventilation system from FIG. 1 , wherein the forces acting onthe valve closing body are marked;

FIG. 11 illustrates an embodiment of a control characteristic of thecrankcase pressure as a function of the vacuum on the outlet side of thepressure control valve of the crankcase ventilation system from FIG. 1 ;

FIG. 12 illustrates an oil separator according to the prior art; and

FIG. 13 illustrates a side view of the oil separator from FIG. 12 ,which is configured according to the prior art.

Identical or similar designs, elements, or features are provided withidentical reference signs in FIGS. 1 to 12 .

DETAILED DESCRIPTION

FIG. 1 illustrates a perspective view of a crankcase 410 (shown onlyschematically), which comprises an oil separator 200 of a crankcaseventilation system. The crankcase 410 is part of an internal combustionengine. The internal combustion engine may be installed in a motorvehicle. The oil separator 200 is configured as an oil separator foroil-containing air from an interior of the crankcase 410. In suchapplications, the oil-containing air is usually mixed with combustiongases exiting from the cylinders as leakage gas into the crankcase. Thismixture is frequently also called crankcase gas, the term “air” stillalso being used for the sake of simplicity.

The oil separator 200 comprises a substantially oval-cylindrical—inparticular, circular-cylindrical—filter housing composed of a firstfilter housing part 210—namely, a housing cover—and a second filterhousing part 220—namely, a housing body. The second filter housing part220 has an inlet 222 for the oil-containing air 500. Arranged in thefilter housing is a filter element 100 comprising at least one filtermedium 10 made of a filter material that has been arranged in an annularshape, e.g., a circular ring shape or an oval ring shape (see FIG. 2 ).The filter element 100 is covered by the filter housing in FIG. 1 , andtherefore is marked with a dashed reference line. Within the filterhousing 210, 220, the air 500 (a corresponding air flow 20 is indicatedin FIG. 2 by an arrow) is filtered by means of the filter medium 10. Theresulting clean air 510 is guided out of an interior 12 (FIG. 2 )enclosed by the filter medium 10, through a clean air discharge element50 of the filter element 100, to a clean air outlet 212 of the housingcover 210, and from the clean air outlet 212 back into the intake ductof the internal combustion engine. Separated oil is removed through anoil outlet 230.

The oil separator 200 has a pressure control valve, in order to limitthe crankcase vacuum to a defined value. The pressure controlvalve—depicted by way of example in FIGS. 2 and 3 —has a valve closingbody 310 that is surrounded by a valve closing body sealing element 320,preferably by a membrane, as is illustrated here.

On the end facing away from the valve closing body 310, the membrane 320is connected to the first filter housing part 210, for example, by beingclipped into the first filter housing part 210. Alternatively, themembrane 320 may also be mounted between the filter housing part 210 andthe cover element 214. Preferably, the membrane is clamped between thefirst filter housing part 210 and an insert 350 forming even morepreferably the lower stop of the spring 330, as in thepresently-described embodiment. The insert 350 has openings, so that theambient pressure can act on the membrane 320 and on the valve closingbody 310.

In order to be closed, the pressure control valve has a valve seat 52arranged on the filter element 100. In contrast to the prior artillustrated in FIGS. 12 and 13 , the filter element 100 illustrated inFIGS. 2, 3, 8, and 10 has a cover element 40 that is configured as anend plate and has a sealing surface 52 at the end thereof that facesaway from the filter element 100, wherein this sealing surface 52 isprovided in order to seal off the pressure control valve 52, 310, 320,330, by the ability of the valve closing body sealing element 320 or thevalve closing body 310 to come into sealing contact with the sealingsurface 52, preferably with a contact surface 312 (see FIG. 6 ) of thevalve closing body 310 or the membrane 320.

The membrane 320 is configured to seal the clean air outlet 212 and theinterior 12 of the filter medium 10 off from the ambient air pressure,and to keep the valve closing body axially movable.

The valve closing body 310 can be moved relative to the valve seat 52,as illustrated in FIG. 10 . The left side of the illustrated sectionalview depicts the closed state of the valve, where the valve closing body310 abuts, preferably axially (as is shown), against the sealing surface52 with a circular ring-shaped contact surface 312 (see FIG. 6 ); on theright side of the view, the valve closing body 310 is spaced apart fromthe sealing surface 52, so that the valve is open. The pressure controlvalve 52, 310, 320, 330 is configured so as to control the flow rate orvolume flow of the fluid flowing away through the clean fluid dischargeelement 50, by means of the movement of the valve closing body 310relative to the valve seat 52, in particular, through the modificationof the cross-section of the flow channel 340 formed by the gap betweenthe sealing surface 52 and the valve closing body 310.

The pressure control valve is configured such that the membrane 320 issubjected to the pressure 600 prevailing in the clean air outlet 212 onthe side thereof facing the filter element 100 or the housing interior,in the region of the circular ring area A_(M) defined by the diametersØ_(M) and Ø_(M), and the valve closing body 310 is subjected to thepressure 610 prevailing in the interior 12 of the filter medium 10 onthe side thereof facing the filter element 100 or the housing interior,in the region of the circular area A_(D) defined by the inner diameterØ_(D) of the sealing surface 52. On the side facing away from the filterelement 100 or the housing interior, the membrane 320 and the valveclosing body 310 are also subjected to the ambient pressure. Preferablyalso provided is a return spring 330 that subjects the membrane 320and/or the valve closing body 310 to a force that acts in a direction ofopening, i.e., is directed away from the filter element 100. At leastone opening in a pressure control valve cover element 214 and/or aninsert 350 causes ambient pressure to be applied to the back side of themembrane; this ventilation makes it possible for the pressure controlvalve to work undamped.

Preferably, a return spring 330—as already described—is arranged on theside of the valve closing body 310 that faces away from the filterelement 100. The return spring 330 subjects the valve closing body 310and/or the membrane 320 arranged thereon to a force 620 (see FIG. 10 )oriented away from the valve seat 52. The compression spring or returnspring 330 services to ensure the rest position of the valve closingbody 310. The rest position corresponds to the position of the valveclosing body 310 at which the force of the return spring 330 is exactlyas great as the sum of the force of the crankcase pressure 610 and theforce of the suction pressure 600.

On the way from the interior 12 of the filter medium 10 to the clear airoutlet 212, the clean fluid flows through a flow channel 340 (see FIGS.3 and 10 ) that is arranged between the valve closing body 310—inparticular, the membrane 320 arranged on the valve closing body 310—andthe valve seat 52, and that preferably has the shape of an annular gap,as is provided presently. The diameter of this flow channel 340 can bechanged or regulated through relative movement of the valve closing body310 to the valve seat 52.

With decreasing pressure in the clean air outlet 212 or on the exit sideof the pressure control valve, the membrane 320 makes a stroke movementin the direction of the valve dome or valve seat 52, thereby reducingthe cross-sectional area of the flow channel 340. This increases theflow resistance of the pressure control valve over the valve seat 52.

The control behavior of the pressure control valve can be adjusted viathe diameter cross-section ratios Ø_(M), Ø_(D) of the membrane 320 andthe inner diameter of the sealing surface 52 or the end surface of theclean fluid discharge element 50 that faces away from the filter element100. FIG. 10 illustrates the cross-section diameter Ø_(M) of themembrane 320 (which, in the present embodiment, is defined by the rollpoint of the membrane 320) and the cross-section inner diameter Ø_(M) ofthe sealing surface 52.

The valve closing body 310 is in the rest position (closed position)when

-   -   a) the force F of the return spring 330    -   b) minus the differential pressure Δp from the atmospheric        pressure and the crankcase pressure 610, multiplied by the        cross-sectional area A_(D) (defined by the inner diameter Ø_(D)        of the valve seat 52)    -   c) minus the differential pressure Δp from the atmospheric        pressure and the suction pressure 600, multiplied by the        cross-sectional area A_(M) (defined by the ring between the        cross-section diameter Ø_(M) of the membrane 320 and the inner        diameter Ø_(D) of the valve seat 52) equals zero.

In summary, this gives:

$\begin{matrix}{0 =} & {F_{{return}\mspace{14mu}{spring}\mspace{14mu} 330} - {F\left( {}_{{crankcase}\mspace{14mu}{pressure}\mspace{14mu} 610} \right)} -} \\ & {F\left( {}_{{suction}\mspace{14mu}{pressure}\mspace{14mu} 600} \right)} \\{=} & {F_{{return}\mspace{14mu}{spring}\mspace{14mu} 330} - {\Delta\;{p\left( {}_{{{atmospheric}\mspace{14mu}{pressure}} - {{crankcase}\mspace{14mu}{pressure}}} \right)}*}} \\ & {A_{D} - {\Delta\;{p\left( {}_{{{atmospheric}\mspace{14mu}{pressure}} - {{suction}\mspace{14mu}{pressure}}} \right)}*A_{M}}}\end{matrix}$

The return spring 330 prevents the membrane 320 from being permanentlyclosed at small suction vacuum pressures 600 from the turbocharger orintake duct of the engine. In addition, the location of the pressurecontrol characteristics can be varied by means of the return spring 330.This means that with a harder return spring 330, the suction vacuumpressure 600 can act more intensely on the crankcase, and the curveshifts downward.

FIG. 11 illustrates an exemplary control characteristic line of apressure control valve. The Y-axis represents the pressure prevailing inthe inlet for pre-filtration fluid 222 or on the pre-filtration side250—in particular, the crankcase pressure—in hectopascals [hPa]. TheX-axis represents the pressure prevailing in the clean air outlet 212—inparticular, the suction vacuum pressure—in hectopascals [hPa]. The firstcontrol characteristic line, represented in FIG. 11 with a solid line,shows the pressure ratios at a volume flow in the pressure control valveof 100 liters per minute. The second control characteristic line,represented in FIG. 11 with a dashed line, shows pressure ratios at avolume flow in the pressure control valve of 20 liters per minute. Thecontrol range of the two control characteristic lines—shown by way ofexample—lies in the range of −2 to −28 hPa. The slope of the ranges ofthe two control characteristic lines marked with the reference signs700, 702 depends on the area ratios A_(D) and A_(M) of the valve seat 52and the membrane 320. The intersection of the two control characteristiclines with the Y-axis, marked with the reference signs 710, 712, showsthe pressure drop with the pressure control valve is open.

As depicted in FIG. 11 , the pressure drop of the oil separator 200 alsoaffects the situation of the pressure control curve, wherein when thepressure drop or volume flow increases, the situation of the pressurecontrol curve rises. Conversely, the crankcase pressure decreases with alower volume flow.

The ratio of the cross-section diameters Ø_(M) and Ø_(D) of the membrane320 and the sealing surface 52 influences the slope 700, 702 of thepressure control curve. If a negative pressure prevails in the crankcaserelative to the atmosphere, and the pretension of the return spring 330is overcome, then the membrane 320 moves onto the sealing surface 52,and the flow resistance increases.

First, if the suction vacuum pressure 600 is large enough and the returnspring 330 is compressed, this results in a curved curve, and finally ina minimum of the crankcase pressure.

At even higher suction vacuum pressures, a slight increase in thepressure 610 is to be observed in the interior 12 of the filter medium,in particular, the crankcase pressure. In these operational ranges, themembrane 320 closes the suction side of the valve intermittently, andthus throttles or interrupts the volume flow. This intermediate pressureis higher than the minimum pressure, because when the valve seat 52 isclosed and there is a strong suction vacuum pressure 600, the pressure610 in the crankcase must be correspondingly higher, in order to for themembrane 320 to again be lifted off from the valve seat 52 against thesuction vacuum pressure acting on the outside thereof.

The oil separator 200 may have an overpressure valve 800 (FIG. 1 ), forsafety reasons. This overpressure valve may be configured, for example,as is described in DE 10 2013 005 624 A1.

FIG. 8 illustrates the components of an embodiment of a filter element100 according to the present invention. This filter element 100 isconfigured for the crankcase ventilation system illustrated in FIG. 1 .The filter element 100 has a cover element, in particular, an end plate40. This end plate 40 covers the covering surface 30 (see FIG. 3 ) ofthe filter medium 10 facing the clean fluid outlet 212, and is connectedsealingly thereto, so that the fluid flows through the filter medium 10into the interior 12 of the filter medium 10. The filter element 100 isan annular coalescence element. For this purpose, the filter element 100has, as preferred, a filter medium 10 configured as a non-woven fabricthat is wrapped repeatedly and thus in a plurality of layers annularlyaround the central tube 70 (also called a support tube). The centraltube 70 allows for flow therethrough and therefore has openings. Thiscan be realized, for example, by a lattice-shaped configuration—as shownin FIG. 8 —by means of a perforated plate or the like. The filter medium10 is a non-woven wrap. For stabilization and sealing, it is preferablysealingly connected at each of the end faces—for example, by means ofgluing or welding—to cover elements 40, 42 configured as end plates. Theconstruction of the coalescence element with the wrapped non-wovenfabric is thus fundamentally different from other filter elements, whichare intended to separate solid particles from fluids such as air or oiland generally have a pleated filter medium.

The sealing surface 52 on the clean fluid discharge element 50 is spacedapart from the axial outer surface of the cover element 40. The axialinstallation space required for the clean fluid outlet 212 is therebybridged. The length of the clean fluid discharge element 50, as measuredfrom the axial, outer surface of the cover element 40, corresponds tothe diameter of the clean fluid outlet 212 of the upper housing part210. This makes it possible to achieve a streamlined overall design withwhich the positioning of the sealing surface 52 on the cover element 40or on the filter element 100 is not accompanied by disadvantages.

The cover element 40 is configured as an end plate of the filter element100, as is preferred, in the embodiment illustrated in detail in FIGS.2, 3, and 8 . The cover element is sealingly and non-releasablyconnected to the filter medium at an end face of the filter element, forexample, by gluing or welding. The cover element 40 is preferablyproduced from thermoplastic polymer, preferably by injection molding.

The clean fluid discharge element 50 is integrally, sealinglyconnected—as is preferred—to the cover element 40 in the embodimentillustrated in detail in FIGS. 2, 3, and 8 .

The clean fluid discharge element 50 is preferably acircular-cylindrical, straight tube, as also illustrated in thedrawings. This tube comprises a closed cylindrical wall and two openends, wherein the sealing surface 52 is configured on one end that facesaway from the cover element, and the other end is connected to the coverelement 40, so that a fluid connection to the interior 12 of the filtermedium 10 or filter body is formed. The ends are preferably oriented soas to be perpendicular to the central axis.

In the embodiment illustrated in detail in FIGS. 2, 3, and 8 , as ispreferred, the cover element 40 is configured as an annular end plateaway from which the clean fluid discharge element 50, configured as atube, extends integrally on the side facing away from the filter medium10. The clean fluid element and the cover element preferably form asubstantially L-shaped or alternatively T-shaped cross-section, as isillustrated.

The crankcase ventilation system has two spaces that must be separatedfrom one another—namely, the pre-filtration space or pre-filtration side250, on which the not-yet-cleaned blow-by gas is located, and thepost-filtration space or post-filtration side 240, on which the cleanedgas is located. In addition, the pre-filtration space 250 andpost-filtration space 240 must also be separated from the atmosphere. Tosolve this problem only with a seal, the filter element 100—illustrated,for example, in FIG. 8 —has a sealing element configured as acombination seal, namely, a filter element seal 60 that makes itpossible to separate all three regions from one another.

The filter element seal 60 (see FIGS. 2, 3, and 8 ) thus serves to sealoff

-   -   the pre-filtration side 250 of the filter element 100 from the        post-filtration side 240 of the filter element 100,    -   the interior of the housing upper part 210 to the ambient air        pressure, and    -   the interior of the housing lower part 220 to the ambient air        pressure.

A special advantage of the filter element seal 60 illustrated in FIGS.2, 3, and 8 over filter element seals from the prior art is thefunctional decoupling of two sealing functions, namely, the sealing offof the interior of the filter housing 210, 220 from the environment onone hand, and the sealing off of the pre-filtration side 250 from thepost-filtration side 240 on the other hand. The two sealing regionsillustrated in FIGS. 2 and 8 —namely, the radially sealing region 64 andthe axially sealing region 66—are functionally independent, butintegrated into one part, namely, the sealing element 60.

The filter element seal 60 illustrated in FIGS. 2, 3, and 8 thus has aregion 64 that is radially compressed by means of a defined force, and aregion 66 that is axially compressed by means of a defined force,wherein the radially compressed region 64 and the axial compressedregion 66 are connected to one another and form a continuous sealingelement, which fulfills two independent sealing functions. The sealingforces are defined by a person skilled in the art, by designing thesealing parameters of Young's modulus, seal dimensions, and sealing gapdimensions.

A defined radial seal can be provided in the oil separator 200illustrated in FIGS. 2, 3, and 8 by radially compressing the filterelement seal 60 by means of a defined force between the housing upperpart 210 and the end plate 40. This is advantageously achieved by theextension of the housing upper art 210 to the height of the end plate40, the end plate 40 thus being arranged over the housing edge of thehousing upper part 210.

The radially sealing region 64 may be configured in the manner of anO-ring (see FIGS. 2 and 3 ). The axially sealing region 66 is, inparticular, configured in the form of a bead having a substantiallyrectangular cross-section, and preferably also has two opposite sealingsurfaces that are in sealing contact with the housing upper part 210 andlower housing part 220, and are compressed axially between the housingparts. In this case, the filter element seal 60 is composed of an O-ringand an axial seal, which are produced in combination.

The spacing apart of the sealing regions 64, 66 is advantageouslyachieved by means of a connecting strut that connects the two sealingregions. The connecting strut preferably has an L-shaped cross-section,as shown in FIGS. 2, 3, and 8 . This signifies that from a first leg andconnecting strut section that forms a hollow cylindrical shape and isconnected to the radially sealing region 64, another leg protrudesradially inward or outward, thus forming a circular annular disc-shapedsecond connecting strut section and connecting to the axially sealingregion 66. This makes it possible for a housing upper part 210 in anarrow installation region to provide independent sealing surfacescorresponding to the sealing regions, e.g., by the housing upper part orhousing cover having a cross-section that is also L-shaped in sectionsin the region of the sealing element 60, wherein the axial leg providesa contact surface for the radially sealing region and the radial legprovides a contact surface for the axially sealing region of the sealingelement.

In the interior 12 of the filter medium 10, a central tube 70 configuredas a support element for the filter medium 10 may be arranged. Thecentral tube supports the filter medium 10 and protects same againstcollapse.

In order to ensure that the fluid flows through the filter medium 10into the interior 12 of the filter medium 10, the filter element 100 hasanother cover element 42—in particular, another end plate 42—on the endthereof that faces the oil outlet 230.

In order to seal off the post-filtration side of the filter element fromthe pre-filtration side of the filter element, another filter elementseal 62—configured, for example, as an O-ring—for sealing off theadditional cover element 42 from the housing part 220 may be associatedwith the additional cover element 42, which is also preferablyconfigured as an end plate, in particular, as an open end plate having acentral opening for the oil drain. This additional filter element seal62 is preferably arranged radially outward on the additional coverelement 42.

FIG. 9 illustrates an exploded view of the components of pressurecontrol arranged in the upper housing part 210. The sealing surface 52is also a component of pressure control. Because the sealing surface 52is arranged on the filter element 100, the sealing surface is depictedin FIG. 8 .

The valve closing body 310 and the membrane 320 perform a verticalstroke movement in the pressure control (see FIG. 9 ). In this verticalstroke movement, the valve closing body 310 and the membrane 320 aremoved to the filter element 100 and away from the filter element.

The components of pressure control illustrated in FIG. 9 include:

-   -   the pressure control element cover element 214, which is        configured to cover the first housing part 210 and has an        opening to the atmosphere;    -   the valve closing body 310;    -   the membrane 320;    -   preferably at least one insert 350 that is arranged between the        membrane 320 and the valve closing body 310 and is configured        for pressure control,    -   the return spring 330; and    -   the first housing part 210.

The return spring 330 is arranged on the side of the valve closing body310 that faces away from the valve seat 52, and is supported down in theinsert 350, which preferably also has an opening. The return spring 330is thus located on the atmosphere side. The valve closing body 310preferably has at least one and particularly preferable—as is presentlyshown—three or four continuations 311 that protrude through at least oneopening of the insert 350. The return spring may thus preferably beaxially mounted between the insert 350 and the continuation orcontinuations 311, in particular, the hooks at the end of thecontinuations. In this manner, the return spring 330 can exert anopening force—in particular, a force oriented away from the sealingsurface 52—on the valve closing body.

FIGS. 12 and 13 illustrate an embodiment of an oil separator 200′ of acrankcase ventilation system according to the prior art. The pressurecontrol of this oil separator 200′ is located on the side of the secondhousing part 220′. The valve closing body 310′ has the form of a dish.The valve seat 52′ is here injection-molded onto the housing outside.The seal between the valve seat 52′ and the valve closing body 310′happens hard to hard, in particular, through identical materials of thetwo components. This combination of identical materials of the valveseat 52′ and the region of the valve closing body 310′ that can bebrought into contact with the valve seat 52′ negatively affects thesealing behavior.

According to an advantageous embodiment, it is provided that the returnspring 330 is located on the atmosphere side in the embodiment of thepresent invention illustrated in FIGS. 1 to 11 . Preferably, the returnspring is protected in a space formed by the membrane 320 and the valveclosing body 310 on one side and by the pressure control valve coverelement 214 on the other side. Arrangement on the outside of the fluidflow protects the spring against the influence of impurities that arecontained in the fluid flow and are deposited on the spring.

In contrast to the filter medium 100 illustrated in FIGS. 2 and 3 , thefluid flows through the filter medium according to the prior art that isillustrated in FIG. 12 from inside to the outside. The direction of flowof the fluid is marked with an arrow.

Instead of a combination seal, the crankcase ventilation systemillustrated in FIG. 12 has two separated O-rings 60″ in order to sealthe post-filtration side 240 of the filter element 100 off from theenvironment and seal the pre-filtration side 250 of the filter element100 off from the post-filtration side 240 of the filter element 100.

LIST OF REFERENCE SIGNS

-   -   10 Filter medium, in particular, non-woven wrap    -   12 interior or cavity enclosed by the filter medium 10    -   20 direction of flow of the fluid to be filtered; in particular,        direction of flow of the pre-filtration fluid 500 flowing        through the filter medium 10, in the present invention (see        FIGS. 2 and 3 )    -   30 Covering surface of the filter medium 10    -   32 Outer surface of the filter medium 10    -   40 Cover element of the filter medium 10; in particular, end        plate of the filter medium 10 that faces the clean fluid outlet        212    -   42 Additional cover element of the filter medium 10; in        particular, end plate of the filter element 100 that faces the        oil outlet 230    -   44 Fastening contour of the end plate 40 configured in order to        fasten the sealing element 60    -   46 Support contour of the end plate 40 (see FIG. 8 )    -   50 Clean fluid discharge element; in particular, dome or nozzle        configured in order to remove the clean fluid—for example, a        tubular clean fluid discharge element    -   52 Sealing surface, in particular, valve seat of the filter        element 100 of the present invention    -   52′ Valve seat in the prior art (FIGS. 12 and 13 )    -   60 Sealing element according to the present invention (see FIGS.        2, 3, and 8 ); in particular, a filter element seal, for        example, to seal the pre-filtration side of the filter element        100 off from the post-filtration side of the filter element 100,        and to seal the interior of the filter housing off from the        environment;    -   60″ Second embodiment for a sealing element, in particular, for        a filter element seal according to the prior art (see FIG. 12 )    -   62 Additional filter element seal; in particular, O-ring    -   64 Radially sealing region of the sealing element 60; in        particular, a compressed region of the sealing element 60 within        the filter housing    -   66 Axially sealing region of the sealing element 60; in        particular, a compressed region of the sealing element 60        between the first housing part 210 and the additional housing        part 220    -   70 Support element, in particular, central tube, of the filter        element 100    -   100 Filter element; in particular, annular filter element, for        example, replaceable filter element or exchangeable element    -   110 Longitudinal axis of the annular filter element 100 or the        housing body 220 (see FIG. 8 )    -   120 Radius of the annular filter element 100 or the housing body        220 (see FIG. 8 )    -   130 Axis of rotation (see FIG. 2 )    -   200 Oil separator of the crankcase ventilation system of the        present invention (FIGS. 1 to 4, 9, and 10 )    -   200′ Oil separator of the prior art (FIGS. 12 and 13 )    -   210 First or upper housing part of the oil separator 200; in        particular, housing cover of the filter housing of the oil        separator 200    -   212 Clean fluid outlet of the oil separator 200 of the present        invention; in particular, clean fluid outlet of the first or        upper housing part 210    -   212′ Clean fluid outlet of the oil separator of the prior art        (FIGS. 12 and 13 )    -   214 Pressure control valve cover element    -   220 Additional, second, or lower housing part of the oil        separator 200 of the present invention (FIGS. 1 to 3 and 10 );        in particular, housing body of the filter housing of the oil        separator 200    -   220′ Lower housing part of the oil separator 200′ of the prior        art (FIGS. 12 and 13 )    -   222 Inlet for pre-filtration fluid, in particular, for        oil-containing gas, for example, for oil-containing air, of the        oil separator 200 of the present invention (FIGS. 1, 2, and 4 )    -   222′ Inlet for pre-filtration fluid, in particular, for        oil-containing gas, for example, for oil-containing air, of the        oil separator of the prior art (FIGS. 12 and 13 )    -   230 Oil outlet    -   240 Post-filtration space or post-filtration side of the filter        element 100 of the present invention    -   240 Post-filtration space or post-filtration side of the filter        element according to the prior art (see FIG. 12 )    -   250 Pre-filtration space or pre-filtration side of the filter        element 100 of the present invention    -   250′ Pre-filtration space or pre-filtration side of the filter        element according to the prior art (see FIG. 12 )    -   310 Valve closing body, in particular, control pin, of the oil        separator 200 of the present invention    -   310′ Valve closing body, in particular, control pin, of the        prior art (FIGS. 12 and 13 )    -   311 Continuations; in particular, hook-shaped continuations        which protrude upward from the valve closing body and with which        the return spring 330 can engage, the continuations preferably        being integral with the valve closing body    -   312 Contact surface of the valve closing body for contacting        with the sealing surface    -   52 of the filter element 100, in particular, in order to close        the valve    -   320 Valve closing body sealing element; in particular, a        membrane surrounding the valve closing body 320, for example, a        membrane extending between the valve closing body 310 and the        first housing part 210    -   320′ Valve closing body sealing element of the prior art (FIGS.        12 and 13 )    -   330 Return spring of the oil separator 200 of the present        invention    -   330′ Return spring of the prior art (FIGS. 12 and 13 )    -   340 Flow channel arranged between the valve closing body 310, in        particular, the valve closing body sealing element 320, and the        sealing surface 52    -   350 Insert configured for pressure control    -   410 Housing of the crankcase ventilation system    -   500 Pre-filtration fluid, in particular, oil-containing gas, for        example, oil-containing air    -   510 Clean fluid, in particular, clean gas, for example, clean        air    -   600 Force exerted through the pressure prevailing in the clean        air outlet 212, in particular, suction pressure, for example,        suction vacuum pressure    -   610 Force exerted through the pressure prevailing in the        interior 12 of the filter medium 10, in particular, the        crankcase pressure    -   620 Force exerted through the return spring 330    -   700 Range of the first control characteristic line where the        slope thereof is dependent on the dimensions, in particular, on        the area ratios A_(M)/A_(D)    -   702 Range of the second control characteristic line where the        slope thereof is dependent on the dimensions, in particular, on        the area ratios A_(M)/A_(D)    -   710 Point of intersection of the first control characteristic        line with the Y-axis, which shows the pressure drop when the        pressure control valve is open    -   712 Point of intersection of the second control characteristic        line with the Y-axis, which shows the pressure drop when the        pressure control valve is open    -   720 Inflection point of the first control characteristic line as        a function of the compression spring or spring rate of the        return spring 330    -   722 Inflection point of the second control characteristic line        as a function of the compression spring of the return spring 330        or the spring rate of the return spring    -   330    -   800 Overpressure valve    -   A_(M) Cross-sectional area of the membrane 320    -   A_(D) Cross-sectional area of the inner diameter Ø_(D) of the        sealing surface 52, or the cross-sectional area of the inner        diameter of the end surface of the clean fluid discharge element        50 facing away from the filter element 100    -   Ø_(M) Cross-section diameter of the membrane 320    -   Ø_(D) Cross-sectional inner diameter of the sealing surface 52        or inner diameter of the end surface of the clean fluid        discharge element 50 facing away from the filter element 100

What is claimed is:
 1. A filter element for an oil separator of a crankcase ventilation system, the filter element comprising: at least one filter medium surrounding a central axis, the at least one filter medium configured to separate oil from aerosol, the at least one filter medium having an axial end surface forming a covering surface extending in a radial direction relative to the central axis; a cover element formed as an annular end plate, fixed onto and fully covering the covering surface of the at least one filter medium; and a tubular projection projecting axially outwardly away from the cover element and the at least one filter medium, the tubular projection having an open interior which opens through the cover element into an interior of the at least one filter medium, wherein the tubular projection is a clean fluid discharge element configured to remove cleaned fluid from an interior of the filter element; wherein an axially outer end of the tubular projection of the filter element has an annular sealing surface forming a valve seat; wherein the tubular projection is configured as a clean fluid discharge element that extends away from the filter element and is configured to remove cleaned fluid from an interior of the filter element to the valve seat of the cover element; wherein the valve seat of the cover element is configured as a sealing surface for a pressure control valve body of the crankcase ventilation system to sealably close against.
 2. The filter element according to claim 1, wherein the filter element is oval-cylindrical; and wherein the filter element has a cavity in the interior of the at least one filter medium; wherein the fluid to be filtered flows from the outer surface of the filter medium to the cavity; and wherein the cavity is connected directly to the clean fluid discharge element in order to remove the cleaned fluid.
 3. The filter element according to claim 1, wherein the clean fluid discharge element and/or the annular sealing surface is formed of at least one mechanically fixed and/or rigid material; wherein the at least one mechanically fixed and/or rigid material is a moldable material selected from the set consisting of: polyurethane, polyamide, or polyamide formed from polyamide 66 with 35% glass fiber (PA 66 GF 35).
 4. The filter element according to claim 1, wherein the annular sealing surface, the clean fluid discharge element, and the cover element are integrally formed as a unitary one-piece component.
 5. The filter element according to claim 1, wherein the at least one filter medium is a multi-layered non-woven wrap.
 6. The filter element according to claim 1, wherein the cover element and clean fluid discharge element are continuously closed.
 7. The filter element according to claim 1, wherein the annular sealing surface of the tubular projection is circular, substantially flat and free of burrs.
 8. The filter element according to claim 1, wherein a circumferential edge of the annular sealing surface of the tubular projection is rounded.
 9. An oil separator for a crankcase ventilation system, comprising: an oil separator housing including: a first housing part; and a second housing part secured to the first housing part and enclosing a chamber therein; a filter element according to claim 1 arranged in the chamber of the oil separator housing; wherein the first housing part includes at least one oil separator clean fluid outlet configured to remove the cleaned fluid; and the pressure control valve is configured to limit the negative pressure applied in the crankcase ventilation system, the pressure control valve formed in combination by: the valve seat of the filter element; and a valve closing body accommodated in the first housing part that operates in conjunction with and sealably closes against the valve seat; wherein the sealing surface of the tubular projection of the cover element of the filter element forms the valve seat against which the valve closing body sealably closes when the pressure control valve is in a closed state.
 10. The oil separator according to claim 9, wherein the valve closing body comprises at least one elastic valve closing body sealing element, at least on a region thereof arranged to contact with the valve seat of the filter element; and wherein the at least on a region of the at least one valve closing body is surrounded by an elastic valve closing body sealing element on the region thereof that is arranged to contact with the valve seat of the filter element.
 11. The oil separator according to claim 10, wherein the valve closing body sealing element is formed out of at least one elastomer; wherein the at least one elastomer are selected from the set: ethylene acrylate rubber (EAR) and/or from acrylate rubber and/or from hydrogenated nitrile rubber (H)NBR.
 12. The oil separator according to claim 9, wherein the valve closing body sealing element is connected fixedly, non-releaseably to the valve closing body; wherein the valve closing body sealing element is applied onto the valve closing body by a spray process.
 13. The oil separator according to claim 9, wherein the valve closing body is flat or level on the region thereof that faces the valve seat and contacts with the valve seat of the filter element.
 14. A method for limiting the crankcase vacuum of a crankcase ventilation system to a predetermined value, comprising: providing an oil separator housing enclosing a chamber therein; providing a filter element configured to separate oil from fluid, including: at least one filter medium surrounding a central axis, the at least one filter medium that is configured to separate oil from aerosol, the at least one filter medium having an axial end surface forming a covering surface extending in a radial direction relative to the central axis; a cover element formed as an annular end plate, fixed onto and fully covering the covering surface of the at least one filter medium; and a tubular projection projecting axially outwardly away from the cover element and the at least one filter medium, the tubular projection having an open interior which opens through the cover element into an interior of the at least one filter medium, wherein the tubular projection is a clean fluid discharge element configured to remove cleaned fluid from an interior of the filter element; wherein an axially outer end of the tubular projection of the filter element has an annular sealing surface forming a valve seat; wherein the tubular projection is configured as a clean fluid discharge element that extends away from the filter element and is configured to remove cleaned fluid from an interior of the filter element to the valve seat of the cover element; wherein the valve seat of the cover element is configured as a sealing surface for a pressure control valve closing body of the crankcase ventilation system to sealably close against; and providing the pressure control valve configured to limit the negative pressure applied in the crankcase ventilation system, the pressure control valve formed in combination by: a valve closing body that operates in conjunction with valve seat of the cover element; wherein the sealing surface of the filter element forms the valve seat against which the valve body closes; arranging the filter element replaceably in the chamber of the oil separator housing; arranging the valve closing body of the pressure control valve in the oil separator housing such that the valve closing body is closeable against the valve seat of the filter element; operating the pressure control valve responsive to prevailing pressure in the crankcase ventilation system to limit the crankcase vacuum such that the valve closing body is moved relative to the filter element and the valve seat of the filter element to control crankcase vacuum.
 15. The filter element according to claim 1, further comprising: at least one annular sealing element of elastic sealing material arranged on the filter element; wherein the at least one annular sealing element is spaced radially away from and closed circumferentially about the central axis of the filter element; wherein the at least one annular sealing element comprises: an axial sealing element having an axial sealing region sealing between and compressed axially between an upper housing part and a lower housing part, when installed in an oil separator housing configured to receive the filter element; and a radial sealing element having a radial sealing region sealing radially between the cover element and a radially inner side of the upper housing part, when installed in the oil separator housing configured to receive the filter element; wherein axial, as used herein, is a direction of the central axis, wherein radial, as used herein, is a direction transverse to the central axis. 